Plastic films find utility in a wide variety of packaging applications such bags, containers, cups, pouches, tubes, and trays. Laminates, single layer films, and multi-layer films having a heat-sealable layer are often used in “form, fill, and seal” (FFS) machines. FFS machines create a continuous stream of packages from the film, the packages capable of being closed by film-to-film seals.
Film-to-film heat seal closures are formed by placing the film between opposing heat seal jaws that apply pressure and also apply heat above the seal initiation temperature of the film. The heat seal closures made are often the strongest after the seal has cooled to ambient temperature. In order to increase production capacity, the packages are filled with product before the heat seal has time to completely cool. Thus, it is necessary for the heat seal closure to provide sufficient strength very rapidly without the need for cooling the package to ambient temperature. Otherwise, the heat seal closure will be compromised resulting in reject product, waste, and added expense.
Moreover, films used in retort packages need to form heat seals that can withstand elevated temperature required for sterilization. Retort packages are typically exposed to temperatures greater than 121° C., or greater than 130° C., for an extended period in order to sterilize the contents therein.
The art therefore recognizes the continuous need to develop improved films for FFS applications. In particular, a need exists for films having a low heat seal initiation temperature and a strong hot tack strength over a broad temperature range in order to increase production efficiency for packaging procedures, such as FFS procedures. A further need exists for films having high temperature seal strength in addition to the aforementioned film properties.